This review contains plot spoilers and is based on the UK preview of the episode.

Given Sky's recent introduction, you might be forgiven for pondering whether Clyde's role in The Sarah Jane Adventures is quite what it once was; he no longer has Luke around as a buddy, and Rani seems more likely to act as a mentor to Sky. Clyde's place in this new incarnation of The Sarah Jane Adventures seems more tenuous than ever before... making it pretty much the perfect time for this sort of story. Because here we get the chance to affirm Clyde Langer's importance to Sarah Jane and Rani, as well as Sky herself cleverly being written as Clyde's main supporter. In essence, these two episodes work extremely well to cement the new team.

We open with Clyde appearing to speak directly to camera, immediately linking us more strongly than usual to the character, and drawing us into identifying with his eventual plight. We begin with a fairly light tone, however, with gags about the fictional character of Suzy June Jones, Alien Slayer, and what must surely be a deliberate homage to The Unearthly Child/Remembrance of the Daleks in the form of Clyde's textbook on the French Revolution. Starting with in-jokes and the poisson sky also provides a counterpoint to later, darker events, giving this story a real sense of light and shade.

But it's Clyde's rapid descent into homelessness that forms the crux of Phil Ford's script. Setting up two puzzles – the totem pole curse and the Night Dragon disappearances – allows these to be effectively contrasted. Whilst one is fantastical, the other is simply a misunderstanding of ordinary life on the streets. Ellie Faber's world may seem like a case for Sarah Jane and the gang, but its mysteries ultimately belong to a different genre: another world where names are taken from posters and pizza boxes, and where identities can shift and change and get worn down without any need for curses or aliens.

Lily Loveless is excellent as Ellie, although Clyde does seem to build a new life for himself rather rapidly, something which slightly takes the edge off episode two's representations of loss. And of course Ellie suffers the curse of the non-regular character, unable to be integrated into Clyde's usual life of family and friends.

The magical power of naming is referenced by this story's title – poor, unfortunate Clyde Langer – but culture is just as important here as naming. Children's television drama might not often focus directly on questions of culture, but that's what Phil Ford aims for. It's London's "Museum of Culture" which houses the creepily dangerous totem pole (itself a sort of “storybook” according to Sarah Jane), while Clyde's interest in the artefact is explained by his love of art. The fragility of culture is later emphasized when Clyde has to use one of his comic book sketches to get a fire going. And the strength of culture as a connection between people is finally restored by Clyde's portrait of Ellie – a work of art that links him to his memories and feelings. Art even offers a possible way off the streets for 'Ellie' and 'Enrico Box', with Clyde suggesting that he can draw for tourists at Covent Garden. References to art and culture are threaded through both episodes: culture is both threat and comfort, a storehouse of ancient powers and a source of present-day hopes. Homelessness might be the story's obvious central topic, but woven through this are quickfire sketches of culture's importance, and of how art and stories and names and belonging can all make life worth living.

There's another vital ingredient, though: reason. Sky continues to ask questions and pick at Clyde's absence because no-one can give her a good enough reason for their sudden new patterns of behaviour. “Psychophonic programming” means that Sarah Jane, Rani, and Clyde's mother have all started to act irrationally, and so Sky keeps on looking for a reason and a proper explanation, like an inquisitive child who can't ever stop asking “why?”

This is a very strong story, made up of striking images such as the fish storm and the animated totem pole, while Daniel Anthony puts in yet another outstanding, charismatic performance, and insistent incidental music helps build a feeling of exotic danger. The Curse of Clyde Langer suggests that there are real limits to what Sarah Jane's gang can achieve – they can defeat aliens but not London's alien domain of homelessness. But it also reinforces values of culture and reason, showing The Sarah Jane Adventures at its most enlightening. Phil Ford hits a definite high point with this tale, and I hope it won't be long until we see his work again in the many worlds of Doctor Who(assuming his name hasn't mysteriously blazed with a special effects' glow and vanished from all credits).